This document is not restricted to specific software and hardware
versions.

The information presented in this document was created from devices in
a specific lab environment. All of the devices used in this document started
with a cleared (default) configuration. If you are working in a live network,
ensure that you understand the potential impact of any command before using
it.

A Destination Unreachable message (Type 1) is generated in
response to a packet that can not be delivered to its destination address for
reasons other than congestion. The reasons for the non-delivery of a packet is
described by code field value. For details of all codes, refer to
RFC 2463
Section 3.1.

Packet Too Big Message

2

0

A Packet Too Big message is sent in response to a packet that
it cannot forward because the packet is larger than the Maximum Transmission
Unit (MTU) of the outgoing link.

If a router receives a packet with a hop limit of zero, or a
router decrements a packet's hop limit to zero, it must
discard the packet and send an ICMPv6 Time Exceeded message with Code 0 to the
source of the packet. This indicates either a routing loop or an initial hop
limit value that is too small. For more details refer to
RFC 2463
section 3.3.

A Parameter Problem message is generated in response to an IPv6
packet with problem in its IPv6 header, or extension headers, such the node
cannot process the packet and must discard it. For more details refer to
RFC 2463
section 3.4.

Routers send out router advertisement message periodically, or
in response to a router solicitation.

Neighbor Solicitation Message

135

0

Nodes send neighbor solicitations to request the link-layer
address of a target node while also providing their own link-layer address to
the target.

Neighbor Advertisement Message

136

0

A node sends neighbor advertisements in response to neighbor
solicitations and sends unsolicited neighbor advertisements in order to
propagate new information quickly (which is unreliable).

Redirect Message

137

0

Routers send redirect packets to inform a host of a better
first-hop node on the path to a destination. Hosts can be redirected to a
better first-hop router but can also be informed by a redirect that the
destination is in fact a neighbor. The latter is accomplished by setting the
ICMP target address equal to the ICMP destination address.

Refer to RFC
2461 for more information on Neighbor Discovery for ICMPv6.